Commander Charles Tucker III was the chief engineer on the ISS Enterprise. Due to the hazardous nature of warp reactor technology, the right side of Commander Tucker's face was deformed, as a result of delta radiation exposure. The deformity was so extreme that it would make sure his "grandkids'll glow in the dark."
Tucker was very attracted to T'Pol and even did her an enjoyable "favor" while she was enduring the pon farr. While under the influence of a mind meld with T'Pol, Tucker unknowingly sabotaged the Suliban cloaking device that he had previously installed on Enterprise. It turned out that T'Pol was using him to help Captain Forrest regain command of the starship. As a result, he spent four hours in the agony booth. He was incensed when T'Pol told him what she done.
Unlike his counterpart in the mirror universe, Tucker was not friendly or easy going. He was mean-spirited, short-tempered with his subordinates, cynical and highly suspicious of others to the point of paranoia at times. He also, unlike his counterpart, was not friends with Major Malcolm Reed. Quite the opposite: the two hated each other. Tucker was infuriated when Commander Archer had Reed and his MACO detachment investigate the sabotage of the Suliban cloaking device, instead of allowing the engineering department to investigate. When Tucker was later thrown in the agony booth by Archer, Reed took great pleasure in overseeing Tucker's torture, and taunted him over his predicament.
Tucker was a member of the assault team that boarded the USS Defiant (NCC-1764). When the Enterprise was destroyed by the Tholians, Tucker worked together with T'Pol, Reed and Archer to power up the Defiant, escape the Tholian base and destroy the Tholian ships.
Archer assigned Tucker as chief engineer on board Defiant, but ran into problems almost immediately. The Defiant was not fully operational in that warp drive was off-line. To make matters worse, Tucker had no idea how to get the warp drive operational, as Defiant was from one hundred years in the future and Tucker was in no way familiar with this futuristic technology. Archer was less then sympathetic when Tucker explained this to him, ordering him to get the ship fully operational soon or he would find another chief engineer. T'Pol suggested that Tucker use the alien workers found on board to help him, as they might be more familiar with the Defiant's technology.
Tucker's dilemma was further compounded when it was determined that Slar, a Gorn foreman that the Tholians used to work on the ship, was stealing key engine components and was killing members of the engineering department. Eventually, Archer hunted down and killed Slar. Subsequently, the components were found and Tucker was able to get the warp drive online so the Defiant could rendezvous with the other Starfleet vessels that were battling the rebel forces.
Later, Tucker was instrumental in saving the Defiant from being destroyed by the ISS Avenger. Tucker had found Phlox sabotaging key ship components such as shields and weapons systems in order to give Avenger a significant advantage. Tucker managed to overpower Phlox and restore shields and weapons systems. His actions were paramount in allowing the Defiant to eventually overtake and destroy Avenger. (ENT: "In a Mirror, Darkly")